The invention relates to a fuel injection pump. With such lifting slide-valve pumps, the volume control or the beginning of injection control is effected by the control of ports via which the pump working space can be connected to the suction space of the pump, namely by the assignment of control edges lying on the pump piston to the control edges lying in the control slide valve. For this reason, the rotational position of the control slide valve with respect to the cylinder liner must be fixed, with the result that, on the one hand, the control slide valve maintains a certain fixed rotational position in relation to the twistable pump piston and that, on the other hand, during basic adjustment, which is effected by slight twisting of the cylinder liner, which is subsequently clamped, the control slide valve is turned with it.
According to the object of such a control slide valve, the latter executes very many lifting cycles, with the result that a high wear load occurs at the guide surfaces of the anti-twist device. Added to this is the fact that, owing to the fuel control performed by twisting of the pump piston, the control slide valve must be guided very exactly in twisting direction, so that a twisting backlash between control slide valve and cylinder sleeve has a great effect on the metering and injection timing accuracy of the fuel, it being possible for even a small backlash to lead to considerable deviations of the actual control from the setpoint control.
In the case of a known fuel injection pump of the generic type (EP-A-0 181 402), a pin is arranged on the wall of the clearance of the cylinder liner, which pin engages in a longitudinal guide groove of the control slide valve, with the result that, upon the axial displacement of the control slide valve, the latter is secured against twisting by pin and guide groove. Disregarding the fact that the distance between pin and piston axis is relatively small, whereby the lever distance preventing the twisting is also relatively short, the pin has only line contact or, with slight inclined position, point contact toward the groove wall, which leads to a relatively rapid wear, with the consequence of the disadvantageous twisting backlash and corresponding deterioration in the control accuracy of the fuel. A further disadvantage consists in that such a pin can be fixed relatively poorly in the wall of the clearance, whereby during a loosening of this pin considerable damages directly on the pump and indirectly on the engine were possible.